finally a quote from yet another book,,,,,
i) Resin Quantity and Quality - Resin production by the glandular trichomes varies. A strain may have many glandular trichomes but they may not secrete very much resin. Resin color also varies from strain to strain. Resin heads may darken and become more opaque as they mature, as suggested by several authors. Some strains, however, produce fresh resins that are transparent amber instead of clear and colorless, and these are often some of the most psycho active strains. Transparent resins, regardless of color, are a sign that the plant is actively carrying out resin biosynthesis. When biosynthesis ceases, resins turn opaque as cannabinoid and aromatic levels decline. Resin color is certainly an indication of the conditions inside the resin head, and this may prove to be another important criterion for breeding.